The present invention relates to demolition equipment and more particularly to heavy duty demolition shears for reducing building and construction materials to scrap for recycling.
Demolition of buildings and steel structures has become important where space is needed to build new structures while the demolishment of such structures must be efficient and be able to reduce all materials to a small enough size for recycling and eventual reuse of metals once melted down and reformed. Burying of scrap materials is simply not even an option anymore. In fact, reprocessing of metal materials from demolition destined for scrap yards for recycling has become a huge business.
Demolition shears have become an important tool for demolition jobs. Bridges and large buildings have significant amounts of metal support, metal reinforced concrete and other metal reinforced structures. Such metal pieces are large and often have multiple connections. Cutting of these metals by saw, grinder or torch has become way too impractical, expensive and hazardous. Demotion shears are used to punch through metals and shear the metal structures into small pieces. In fact, metal demolition shears are used to cut metal cables, reinforced concrete, car parts, rods, rebar, rail cars, tanks, pipes, channels and other vehicle frames. Demolition shears can easily shear up to sixteen inch I-beams into small pieces that are only a couple of feet long or less and readily usable for recycling once reduced in size.
Demolition shears are typically mounted on the distal end of a boom structure or dipper stick on a backhoe or excavator. By this arrangement, the shear is actually mobile and capable of moving about a demolition site as well as reaching elevated positions up high in a safe manner. The operation of the shears with one movable and one fixed (or movable) jaw is by hydraulic cylinders.
Prior art FIGS. 1 through 3 generally show the structure of a demolition shear. A prior art heavy duty demolition shear 10 has a lower jaw 12 and pivot 14. The lower jaw 14 has a shear blade side 16 with a shear blade 18, a guide blade side 20 with a distal shear blade 22 and a cross, tie or chin plate 24 with a cross blade 26 forming a recess 28 therebetween.
A movable upper jaw 30 is connected to the lower jaw 12 at pivot 14. A hydraulic cylinder or actuator (not shown) also is connected to the shear frame rearward of the lower jaw 12 and a rear portion of the upper jaw 30 The upper jaw 30 has a shear blade side 32 with a shear blade 34, a guide blade side 36 with a distal end shear tip or tang 38. The tang 38 has a front edge 38a, side faces 38b, top seat 38c, rear seat 38d and bottom seat 38e. Bolt holes or apertures 40 pass through the side faces 38b. Replaceable L-shaped shear tip sections 42 have a top vertical section 44 and a bottom horizontal section 46. Replaceable shear tip sections 42 are secured to tang 38 through the apertures 40 with bolts 48 or the like.
In operation, the upper jaw 30 passes into the recess 28. The tip sections 42 need to be periodically replaced as the shear tip becomes worn as it punches through material to be reduced and further shears along the distal shear blade 18, distal guide shear blade 22 and cross cutter blade 26. Also over time, the upper jaw distal end or tang 38 becomes worn as shown in exaggeration in FIG. 1A. The tang side faces 38b wear down as the tang 38 actually becomes thinner and the top vertical sections tend to move inward (arrow A) while the bottom horizontal sections move outward (arrow B). Also tang surfaces 38a, 38c, 38d and 38e can wear with continued use of the shear. Gaps 48 begin to appear between the tang 38 and the shear tip sections 42 This situation detrimentally causes the shear tip portions 42 to break as they strike in operation the distal lower shear blade 18, distal guide blade 22 and cross blade 26.
Total clamping force action between the shear tip or tang 38 and the shear tip sections 42 is also absolutely required for the shear tip and tang to work properly together and for the tang 38 to not wear out prematurely. When the tang 38 and shear tip sections lose complete and total clamping force between the shear tip tang 38 and the shear tip sections or pieces 42, the tang 38 must be cut off and replaced by welding with a new tang 38. It can be costly to replace these worn parts and such repair efforts require the shear 40 to be taken out of operation.
There is a need for a shear tip that encompasses or encapsulates most of the tang that is substantially one-piece with a side plate and is adjustable with one or more shims, to insure complete and total clamping force between the shear tang and the shear tip pieces and to minimize tang side face wear and assure proper alignment of the shear tip on the tang to avoid shear tip breakage.